Cryptogenic acute limb ischemia: a retrospective cohort study defining a previously undescribed clinical entity.

Acute limb ischemia (ALI) is generally secondary to cardioembolism or progression of peripheral vascular disease, however, a discrete population of patients with ALI exists in which no precipitant is ever established. Unlike cryptogenic arterial occlusion in other arenas, such as cryptogenic stroke, cryptogenic acute limb ischemia (cALI) has not been well-described, and no routine management has been established. The aim of this study is to describe patients with cALI, and the risk of recurrence based on the treatment they received. We performed a retrospective cohort study of patients evaluated for ALI at a single academic center, excluding patients with known peripheral artery disease, polytrauma, critical illness, or a history of recent vascular access. Out of 608 individual patients analyzed, 37 were deemed to have cALI on their initial presentation. After extended follow up, 29 patients were eventually found to have a precipitating cause, with 8 patients remaining cryptogenic. On follow up, the overall rate of recurrent ALI was 13% in the group eventually found to have a precipitating cause, and 25% in the cALI group. The median time to recurrence was 16.5 months in the precipitated acute limb ischemia (pALI) group, and 23.3 months in the cALI group. Of pALI patients who recurred, 40% did so despite being therapeutic on anticoagulation. None of the recurring cALI patients were therapeutically anticoagulated. Based on our analysis, nearly 20% of patients presenting with ALI in the absence of known risk factors will remain cryptogenic. Rates of recurrent ALI in patients who present with cALI are significant, particularly in patients who are not maintained on anticoagulation. This suggests that the etiology of ALI in patients without peripheral vascular disease may not have a strong bearing on treatment decisions, and that indefinite anticoagulation may be warranted in patients with no obvious cause on presentation. Future studies are needed to better gauge the risk for bleeding complications and to provide a better understanding of the risks and benefits of recurrence and complications of anticoagulation over time.